Terpenes for reducing the effect of pheromone on lepidoptera

ABSTRACT

The use of terpenes for reducing the pheromone action on Lepidoptera and a method which allows terpenes to act on the habitat of the Lepidoptera are described.

This application is a 371 of PCT/EP96/02391, filed on Jun. 3, 1996.

The present invention relates to the use of terpenes for reducing thepheromone action on Lepidoptera, and to a method which allows terpenesto act on the habitat of the Lepidoptera.

The use of pheromones, in particular mixtures of components of sexpheromones, in the control of Lepidoptera, which comprise harmfulinsects such as grape moths, codling moths, summer fruit tortrix moths,oriental fruit moths, cotton bollworms, peach twig borers, clearwingmoths and leafworms, belongs to the prior art.

Sex pheromones are sex attractants which are produced and secreted intothe environment, in the case of Lepidoptera, by female or male animalswhich are ready to mate and attract male or female Lepidoptera of thesame type.

Fundamentally, there are three different possibilities of using sexattractants in crop protection:

pheromone traps, equipped with synthetic sex attractant lures, aresuspended in potential areas of attack. The capture of male moths in thetraps furnishes proof of the occurrence of this pest. It is an importantaid in integrated crop protection for determining a suitable date forcontrol using conventional methods (monitoring technique).

by combination of an attractant with insecticidal active compounds.There is the possibility of adding insecticides to the lure or the trapor else of treating only the immediate surroundings of the trap. Thelargest part of the male moth population attracted from a wide range canthus be killed (capture technique). The biotope loading is reduced to ajustifiable extent.

by the method of saturating the airspace with sex attractants orsimilarly acting substances. The male butterflies are interrupted fromfinding the females and thus the mating of the animals is prevented. Inthis case, a relatively large amount of the attractant is distributeduniformly in the airspace in the total area of the plant crop to beprotected such that the males can sense the presence of the attractanteverywhere and their normal orientation behavior is disturbed.

Even in this last-mentioned procedure for the use of sex attractants,only comparatively small amounts of the active compounds, which oftenonly correspond to fragments of the customary doses of the classicinsecticidal active compounds, are needed. (Birch (ed.): PheromonesNorth Holland Publ. Co. (1974)). What is concerned here is an extremelyselective, nontoxic control method with the greatest possible protectionof the nontarget organisms, in particular the useful animals. However,the natural sex attractants which are produced by the appropriate organsof the female animals are often accessible with difficultysynthetically.

In a method for the prognosis of the occurrence of Lobesia, the Lobesiasex attractant E7,Z9-dodecadienyl-1-acetate, applied as lures in traps,is used in viticulture as described in DE Patent 24 40 759. Specificcontrol of the grape berry moth has been possible in practice since 1994using the known sex attractant E7,Z9-dodecadienyl-1-acetate.

Laboratory and small-scale experiments for affecting Lobesia botranamales by the confusion technique using the original sex attractant,E7,Z9-dodecadienyl-1-acetate, and using similar substances, namelyZ9-dodecenyl-1-acetate, E7-dodecenyl-1-acetate andE7,E9-dodecadienyl-1-acetate, have been carried out with varying success(ROEHRICH et al., Ann. Zool. Ecol. quim. 1979, p. 659 ff. and thesources indicated there, GUREVITZ and GOTHILF, Phytoparasitica 10 p. 140(1982)).

DE-C 36 03 377 describes a mixture of Z9-dodecenyl-1-acetate andE7-dodecenyl-1-acetate for controlling Lobesia botrana.

It is common to all the methods described that pheromones are alwaysused which attract the Lepidoptera.

Helmut Snoek in Duftstoffe, p. 36, Eigenverlag 1992, describes anotherroute by confusing the insect female with ethereal oils so that it doesnot find the test plant necessary for laying eggs. On p. 39, however,Helmut Snoek comes to the conclusion that large-area monocrops cannot beeffectively protected by aromatic products.

It was an object of the present invention to make available furthermethods for controlling Lepidoptera effectively. Surprisingly, it hasbeen found that the pheromone action on Lepidoptera can be reduced usingterpenes.

Terpenes suitable for the present invention are acyclic, monocyclic andbicyclic terpenes, sesquiterpenes, diterpenes and mixtures thereofincluding E and Z isomers thereof or optical antipodes thereof.

Suitable acyclic terpenes include terpene hydrocarbons such as ocimene,myrcene, terpene alcohols such as geraniol, nerol, linalool,citronellol, nerolidol, prenol (dimethylallyl alcohol),tetrahydrolinalool, geranylgeraniol, 2,6-dimethylheptan-2-ol, terpenealdehydes such as citral, neral, citronellal, tetrahydrocitronellal(2,5,7,7-tetramethyloctanol), terpene ketones such as α-ionone,β-ionone, geranylacetone, phytol, isophytol, retinal and mixturesthereof.

Suitable monocyclic terpenes include monocyclic terpene hydrocarbonssuch as α-terpinene, γ-terpinene, terpinolene, α-phellandrene,β-phellandrene, limonene, dipentene, monocyclic terpene alcohols such asmenthol, α-terpineol, 1,8-terpine, monocyclic terpene ketones such asmenthone, pulegone, carvone and mixtures thereof.

Suitable bicyclic terpenes include the carane group with carane, caroneand carvenone, the pinane group with pinane, α-pinene and β-pinene andthe bornane group with bornane and camphor, and mixtures thereof.

Suitable sesquiterpenes include the acyclic sesquiterpenes such asfarnesol, nerolidol, monocyclic sesquiterpenes such as bisabolene,bicyclic sesquiterpenes such as cadinene, β-selinene, tricyclicsesquiterpenes such as α-santalene, and mixtures thereof.

Suitable diterpenes include phytol, isophytol, retinal and mixturesthereof.

Those preferred are citral, nerolidol, prenol (dimethylallyl alcohol),tetrahydrolinalool, geranylgeraniol, 2,6-dimethylheptan-2-ol, neral,citronellal, tetrahydrocitronellal (2,5,7,7-tetramethyloctanol),geranylacetone, phytol, isophytol, retinal and mixtures thereof.

Those particularly preferred are citral, nerolidol, prenol(dimethylallyl alcohol), tetrahydrolinalool, geranylgeraniol,2,6-dimethylheptan-2-ol, neral, citronellal, tetrahydrocitronellal(2,5,7,7-tetramethyloctanol), geranylacetone and mixtures thereof.

Those furthermore preferred are citral, neral, citronellal,tetrahydrocitronellal (2,5,7,7-tetramethyloctanol), geranylacetone andmixtures thereof.

In the context of the present invention, citral has proven to be veryparticularly effective.

Both liquid and solid preparations are suitable for formulation,according to the invention, of the terpenes. Suitable solvents arehigh-boiling, aromatic, aliphatic or cycloaliphatic compounds. Besidehydrocarbons, esters, ethers, silicone oils or ketones are particularlyhighly suitable. Typical representatives of these classes are, forexample: xylene, methylnaphthalenes, liquid paraffins, cyclohexanone,ethyl glycol acetate, isophorone and dibutyl phthalate. These solventscan be used on their own or as mixtures with other components. Solutionsin vegetable, animal or synthetic oils or fats and otherevaporation-inhibiting solvents of low vapor pressure, eg. higherC₁₀-C₂₀-alkyl acetates or straight-chain or branched C₁-C₈-dialkylphthalates, can furthermore be prepared for the purposes of prolongingthe action.

The terpenes can furthermore also be used as a mixture with pheromonesand related aromatic substances. Suitable pheromones are described, forexample, in Heinrich Arn, List of Sex Pheromones of Lepidoptera andRelated Attractants, Organisation Internationale de Lutte BiologiqueSection Regionale Ouest Palearctique, 1986.

Examples of suitable pheromones are Z9-dodecenyl-1-acetate,Z8-dodecenyl-1-acetate, E7-dodecenyl-1-acetate, E5-decenyl-1-acetate,E5-decen-1-ol, E7,Z9-dodecadienyl-1-acetate, Z11-tetradecenyl-1-acetate,Z9-tetradecenyl-1-acetate, Z8-tetradecenyl-1-acetate,E8,E10-dodecadien-1-ol, Z3,Z13-octadecadienyl-1-acetate andE2,Z13-octadecadienyl-1-acetate.

If pheromones and related substances are additionally used,E7,Z9-dodecadienyl-1-acetate, Z9-dodecenyl-1-acetate,E7-dodecenyl-1-acetate and mixtures thereof are preferred.

If pheromones and related substances are additionally used, mixingweight ratios of terpene:pheromone of from 100:1 to 1:100, preferably100:2 to 1:50 and particularly preferably 100:5 to 1:10, veryparticularly preferably 100:10 to 1:1, have proven suitable.

For application of the terpenes, dispensers are used which release theactive compound over a long period with a constant release rate. Manysuch systems have already been described in the literature and can bearranged in two categories:

1. matrix systems

2. reservoir systems.

In matrix systems, the active compound is dispersed homogeneously in amatrix. The release rate, due to this means of construction, isnonlinear, but decreases with time. In the case of the reservoirsystems, the active compound is situated in a reservoir and is given offby diffusion through a wall of constant thickness. In contrast to thematrix systems, reservoir systems therefore have a more constant releaserate and are superior in release characteristics and often also in theduration of release.

In the case of the matrix systems, the terpenes are bound in or onnatural or synthetic solid carriers such as rubber, cork, cellulose,plastics, ground carbon, wood meal, silicates, pumice grit, calcinedclay or similar solid carriers. Reservoir systems include specialcapsule formulations, plastic containers, capillaries or other vessels,the active compound being evaporated through films or narrow openings,particularly uniform scent concentrations being achieved over relativelylong periods. Multilayer platelets made of plastic or cellulose, flakes,are also suitable.

Suitable plastic containers are described in DE-A 36 40 880 and EP-A 496102 and EP-A 540 932.

The terpene content in formulations can vary within wide limits.Generally, the ratio of terpene : additive can be, for example, in therange from, for example, 10:1 to 1:10³. In capsule formulations or othersuitable containers, the terpene, for example, can be used in pure,undiluted form and its proportion by weight, based on the totalformulation, can be very high and up to 90%. In general, however, verylow active compound concentrations in the formulations are sufficient inorder to exert the desired action on Lepidoptera. A quantitative ratioof terpene:additive of from 1:3 to 1:10² is preferred.

The terpenes can also be applied in comparatively high concentrations.For this method, formulations having poorly volatile additives whichgive off the terpenes over a sustained period are best suited, such asrubber, cellulose, wax, polymers or evaporation-inhibiting, poorlyvolatile oils or paraffins, and also formulations in capsules or othercontainers (capillaries) which give off the terpenes either throughtheir wall or through narrow openings. The terpene concentration here isin general in the range from 1:1 to 1:10³.

EXAMPLE 1

Laboratory Wind Tunnel

4 electric traps up to 2 cm³ in size were installed in a laboratory windtunnel. As electric traps, commercially available electric insectcapture appliances were rebuilt to give recording lure traps. Thefluorescent tube normally responsible for the attractant action wasreplaced by a scent source.

To avoid positional effects, the four traps were fixed. The wheel rimwas rotated by means of a motor having a speed of two revolutions perhour (once around its own axis and back), so that the traps continuouslychanged position.

With the same lure a preference for certain traps was not found:downwind from 50 to 500 (depending on the directly available amount, asa rule from 200 to 300) Lobesia males of age from one to three days wereset free, these flew specifically to the scent sources contained in thetraps.

The number of moths trapped in each case was determined daily. By meansof the number of moths trapped in the individual traps, theattractiveness of the particular lure was determined (preference test).

The influence of various dilutions of E7,Z9-dodecadien-1-yl acetate wasdetermined by setting the number of moths in the most common trap equalto one; the capturing ability of the other traps was calculated relativeto this.

The scent sources used were cartridges (single-use syringes made ofpolypropylene; content: 1 ml). Filter papers of edge length 4 mm×60 mmwere impregnated with 30 μl of the respective test substance and placedin the syringes, which were then closed with an injection needle (0.9 mmexternal diameter).

A stream of air of velocity 67 ml/min was passed through thesecartridges.

To investigate the action of terpenes, the recapture rate of thecartridges which were lured with 30 μl of E7,Z9-dodecadien-1-yl acetatein a concentration of 10⁻⁴ g/g of silicone oil as a standard or with thesame amount of standard and citral in 10⁻¹ g/g of silicone oil wascompared.

The recapture rate is the ratio of the number of captured Lobesia malesand the number of Lobesia males set free.

The recapture rate of the standard was set equal to one and that of thetraps with the terpene additive was calculated relative to this.

For the traps with addition of citral, an inhibition of the recapturerate in the citral-containing cartridges of 90% resulted.

EXAMPLE 2

Outdoor Wind Tunnels

In spring 1994 two outdoor wind tunnels were built over a row of vinesin each case in an experimental field of the SLFA Neustadt. These werealuminum scaffoldings 2 m high, 2 m wide and 10 m long.

The front and back were covered with mosquito nets made of cotton (meshwidth 1.5×1.5 mm); 50μ thick polyethylene film lay over the entirelength.

Air was blown into the interior through a ventilator at the front of thetunnel.

Two traps each were attached at a height of approximately 60 cm in theinterior of the two wind tunnels on the ventilator side. The traps werelured with E7,Z9-dodecadien-1-yl acetate. Tunnel 1 remained untreatedand served as a control. To simulate a mating disruption situation, 10filter papers were uniformly distributed at various heights (20-120 cm)in tunnel 2 along the row of grapevines. 1 ml of citral solution insilicone oil with a dilution of 10⁻¹ g/g was in each case added dropwiseto these in order to achieve a uniform concentration of the substance inthe interior. A specific number of Lobesia males were in each case setfree on the sides of the two wind tunnels opposite to the ventilatorsides. After the end of the experiment, the Lobesia males captured inthe traps were counted and the recapture rate was determined.

Recapture rate Tunnel 1 0.18 (control) Tunnel 2 0.01 (treatment withcitral)

This means an inhibition of the recapture rate by 94.5%.

We claim:
 1. A method of disturbing the mating of Lepidoptera, whichcomprises reducing the pheromone action and thereby detracting the malespecies of Lepidoptera by treating the habitat of the Lepidoptera withan effective amount of citral and a pheromone and/or a pheromone relatedattractant.
 2. The method of claim 1, wherein the citral is applied tothe habitat as a mixture with an additive selected from the groupconsisting of the organic solvents, vegetable oils, animals oils,synthetic oils and mixtures thereof.
 3. The method of claim 1, whereinthe pheromone or the pheromone related attractant is selected from thegroup consisting of E7,Z9-dodecadienyl-1-acetate,Z9-dodecenyl-1-acetate, E7-dodecenyl-1-acetate, E7,Z9-dodecadien-1-ol,Z9-dodecen-1-ol, E7,Z9-dodecadien-1-al, Z9-dodecen-1-al and mixturesthereof.
 4. The method of claim 1, wherein the pheromone and/or thepheromone related attractant is selected from the group consisting ofE7,Z9-dodecadienyl-1-acetate, Z9-dodecenyl-1-acetate,E7-dodecenyl-1-acetate and mixtures thereof.
 5. The method of claim 1,wherein citral and the pheromone and/or the pheromone related attractantis applied in a weight ratio of from 100:1 to 1:100.
 6. The method ofclaim 5, wherein the weight ratio of citral to the pheromone and/or thepheromone related attractant is from 100:2 to 1:50.
 7. The method ofclaim 5, wherein the weight ratio of citral to the pheromone and/or thepheromone related attractant is from 100:5 to 1:10.
 8. The method ofclaim 5, wherein the weight ratio of citral to the pheromone and/or thepheromone related attractant is from 100:10 to 1:1.